In the field of digital data storage systems, most commercial computers employ Winchester-type disk drives to store application program software and related data. The predominant commercial hard disk drive standard is referred to as the 51/4" disk drive. A new standard has emerged, which is commonly referred to as the 31/2" disk drive, which can store considerably more data in a substantially smaller configuration as compared to earlier 51/4" disk drives. Each 31/2" hard disk, for example, is capable of storing in excess of one gigabyte of information, which is equivalent to eight billion bits of information.
In a digital disk drive storage system, digital data is stored in the form of magnetic energization on a series of concentric, closely spaced tracks comprising the surface of the magnetizable rigid hard disks. Data is applied to, and retrieved from, the rotating disks by magnetic heads which are mounted on a head positioner assembly, and shifted from track to track by the energization of a magnetic coil assembly. Alignment of the magnetic coil assembly and the head positioner mounting surfaces is critically important as any degree of positional shifting at the mounting interface may cause read and/or write errors of varying severity.
A magnetic head positioner assembly typically comprises a central rotating positioner body including a plurality of rigid integral positioner arms with magnetic read/write heads being mounted resiliently or rigidly on the extreme ends of the positioning arms. The positioning arms are interleaved into and out of the stack of rotating magnetic disks typically by means of a magnetic coil assembly mounted to the main body of the head positioner. The coil normally interacts with a permanent magnet structure, and the application of current to the coil in one polarity causes the head positioner arms and heads to shift in one direction, while current of the opposite polarity shifts the head positioner arms and heads in the opposite direction.
A common mounting scheme involves a plurality of mounting screws, typically four such screws, which secure the magnetic coil assembly to the head positioner body. The four screw attachment scheme is intended to minimize misalignment between the magnetic coil assembly and head positioner body which adversely affects the read and write performance of the disk drive unit and which, over time, may ultimately result in the failure of the disk drive unit. However, designs which employ four or more mountings screws typically exhibit poor mechanical resonance characteristics and often involve increased inertia associated with the additional mass of the screws. Moreover, such designs require costly and time consuming alignment procedures to properly mount the magnetic coil assembly to the head positioner body, and often require additional alignment features such as guide pins and the like. Mechanical resonance and head positioning performance suffer as additional alignment features are added to the mounting surfaces. Such designs also require expensive and time consuming machining which is necessary to produce head positioner body and/or the magnetic coil assembly mating surfaces having a high degree of precision.
As disk drive storage capacities and disk rotational velocities continue to increase, it becomes critically important that the magnetic read/write heads be accurately positioned, and that the heads are not subject to undesired shifting in their position as a result of mechanical misalignment of the head positioning apparatus which is subject to mechanical and thermal cycling.
Accordingly, a principal object of the present invention is to provide an improved magnetic head positioner assembly with high precision, self-aligning coil assembly and head positioner mounting surfaces providing greater accuracy and consistency in the positioning of the magnetic heads despite vibration, thermal cycling, and the like.